Saturday, March 1, 2014

New paper finds lows of Arctic sea ice in 2007 and 2012 were due to storms

A new paper published in The Cryosphere finds that the 2 recent lows in Arctic sea ice over the past decade during 2007 and 2012 were strongly related to storm activity, rather than a long-term effect of climate change. According to the authors, "Strong summer storms on the Siberian side of the Arctic Ocean may have been important contributions to the recent [Arctic sea ice minimums] in 2007 and 2012." Arctic sea ice strongly rebounded in 2013 by up to 78% in comparison to 2012, suggesting the 2007 and 2012 lows were just natural variation.

A. Kriegsmann1,* and B. Brümmer11Meteorological Institute, University of Hamburg, Hamburg, Germany*now at: Climate Service Center, Hamburg, GermanyAbstract. This study investigates the impact of cyclones on the Arctic Ocean sea ice for the first time in a statistical manner. We apply the coupled ice–ocean model NAOSIM which is forced by the ECMWF analyses for the period 2006–2008. Cyclone position and radius detected in the ECMWF data are used to extract fields of wind, ice drift, and concentration from the ice–ocean model. Composite fields around the cyclone centre are calculated for different cyclone intensities, the four seasons, and different sub-regions of the Arctic Ocean. In total about 3500 cyclone events are analyzed. In general, cyclones reduce the ice concentration in the order of a few percent increasing towards the cyclone centre. This is confirmed by independent AMSR-E satellite data. The reduction increases with cyclone intensity and is most pronounced in summer and on the Siberian side of the Arctic Ocean. For the Arctic ice cover the cumulative impact of cyclones has climatologic consequences. In winter, the cyclone-induced openings refreeze so that the ice mass is increased. In summer, the openings remain open and the ice melt is accelerated via the positive albedo feedback. Strong summer storms on the Siberian side of the Arctic Ocean may have been important contributions to the recent ice extent minima in 2007 and 2012.